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Kinetic and Mechanistic Studies on the Removal of Cyanotoxins and Antibiotics with Hydroxyl and Sulfate Radical Based Advanced Oxidation Processes

He, Xuexiang
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406881518

Abstract Details

2014, PhD, University of Cincinnati, Engineering and Applied Science: Environmental Engineering.
Chemical contaminants occurring naturally or derived from human-related activities in sources of drinking water have been associated with a wide array of adverse human and ecological health effects. Global climate change, eutrophication and rampant use of pharmaceuticals will likely exacerbate contamination of sources of drinking water. Alternative sustainable approaches such as advanced oxidation processes (AOPs) are desirable for the production of safe drinking water. In this dissertation, the degradation and structural transformations of cyanobacterial toxins (microcystins and cylindrospermopsin) and antibiotics (ampicillin, penicillin VK, piperacillin and cephalothin) were investigated by hydroxyl and sulfate radicals generated by UV-254 nm AOPs. Tap water and natural water samples from East Fork Lake and Toledo Water Plant in Ohio, Lake Erie in Michigan and St. Johns River in Florida, as well as samples from different water treatment stages from a drinking water treatment plant were used as water matrices to evaluate the application of the AOPs. A final concentration of microcystin-LR (MC-LR) below the safe guideline value of 1 µg L?1 was achievable by UV/H2O2 with 80 mJ cm?2 of UV fluence and 882 µM [H2O2]0 when common radical scavengers such as alkalinity and natural organic matter (NOM) were present. The UV/HSO5? treatment efficiency of cylindrospermopsin (CYN) was enhanced in tap water in the presence of trace transition metals, suggesting that the transition metals in natural waters could be important for the effectiveness of the AOPs. Hydroxylation appeared to be the main reaction pathway during the hydroxyl radical reaction with CYN. The oxidation of secondary alcohol, the formation of a double bond in a conjugation with guanidine group, the cleavage of uracil moiety, as well as the elimination of sulfate group were also observed. Steady-state radical concentrations were estimated revealing a non-negligible contribution of hydroxyl radical in UV/S2O82-. The tert-butyl alcohol (a hydroxyl radical scavenger) was thus added in UV/S2O82-, yielding byproducts that indicated specific sites in CYN preferentially attacked by sulfate radicals (SRs). The selective nature of SR species produced a number of byproducts different from those of hydroxyl radical, although both radical species share similarities in the intermediate radical species. Various byproducts were identified in UV/H2O2 process. Both isomerization and photohydration byproducts were observed in UV only process for all the four MCs (i.e., MC-LR, MC-RR, MC-YR and MC-LA); while in UV/H2O2, hydroxylation, hydroxyl addition and diene-Adda double bond cleavage byproducts were detected. The presence of a tyrosine in MC-YR significantly promoted the formation of monohydroxylation byproduct m/z 1061. It was suggested that the difference in the amino acid variables of MCs influenced not only the degradation kinetics but also the reaction mechanisms. The selected antibiotics (i.e., ampicillin, penicillin, piperacillin and cephalothin) were successfully degraded by UV/H2O2 and UV/S2O82- AOPs, though with a slower formation of sulfate anion in UV/H2O2 and a much slower reduction in total organic carbon contents. The transformation mechanisms were also investigated showing the destruction of the ß-lactam ring with a potential subsequent decrease of the antibiotic activity of the treated waters.
Dionysios Dionysiou, Ph.D. (Committee Chair)
Armah de la Cruz, Ph.D. (Committee Member)
Margaret Kupferle, Ph.D. P.E. (Committee Member)
George Sorial, Ph.D. (Committee Member)
243 p.
Environmental Engineering
advanced oxidation processes; microcystin-LR; cylindrospermopsin; hydrogen peroxide; persulfate; peroxymonosulfate

Recommended Citations

Citations

  • He, X. (2014). Kinetic and Mechanistic Studies on the Removal of Cyanotoxins and Antibiotics with Hydroxyl and Sulfate Radical Based Advanced Oxidation Processes [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406881518

    APA Style (7th edition)

  • He, Xuexiang. Kinetic and Mechanistic Studies on the Removal of Cyanotoxins and Antibiotics with Hydroxyl and Sulfate Radical Based Advanced Oxidation Processes. 2014. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406881518.

    MLA Style (8th edition)

  • He, Xuexiang. "Kinetic and Mechanistic Studies on the Removal of Cyanotoxins and Antibiotics with Hydroxyl and Sulfate Radical Based Advanced Oxidation Processes." Doctoral dissertation, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406881518

    Chicago Manual of Style (17th edition)

ucin1406881518
702
© 2014, some rights reserved.Creative Commons License Kinetic and Mechanistic Studies on the Removal of Cyanotoxins and Antibiotics with Hydroxyl and Sulfate Radical Based Advanced Oxidation Processes by Xuexiang He is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.